This CL do a pure rename work as the base of External memory
service refactory.
Bug: dawn:1593
Change-Id: If9595e8d8be97f5eb725acff8891e0bd1baf8928
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/125480
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Shaobo Yan <shaobo.yan@intel.com>